"Slow Reacting Substance of Anaphylaxis" (SRS-A) has been shown to be a highly potent broncho-constricting substance which is released primarily from mast cells and basophils on antigenic challenge. SRS-A has been proposed as a primary mediator in human asthma. SRS-A, in addition to its pronounced effects on lung tissue, also produces permeability changes in skin and may be involved in acute cutaneous allergic reactions. Further, SRS-A has been shown to effect depression of ventricular contraction and potentiation of cardiovascular effects of histamine.
The recent discovery of the naturally occurring leukotrienes and their relationship to SRS-A has reinforced interest in SRS-A and other arachidonate metabolites. SRS-A derived from mouse, rat, guinea pig and man have all been characterized as mixtures of leukotriene-C.sub.4, represented below as structural formula (LT--C.sub.4) and leukotriene-D.sub.4, represented below as structural formula (LT--D.sub.4). ##STR1##
Leukotriene-A, represented below by the structural formula (LT--A), is believed to play a central role in natural conversion of arachidonic acid to the leukotrienes C.sub.4 and D.sub.4. ##STR2##
Leukotriene A has been converted to leukotrienes C.sub.4 and D.sub.4 via methods well known in the art. Synthetic leukotrienes have shown the same biological activities of their naturally occurring counterparts.